On the 60, the screws can be redone any number of times no problem. Definitely not a one-shot situation. The rests have a metal back plate with holes in them through which screws screw into the wood. If you make your own rests, you can choose the screws and the holes into which they screw.
Just for testing, just now I rotated one of the wrist rests and tried a comically long rest. The cantilevering is real, and I would not recommend this 8.5cm extension, but if you get the riser, it has a bunch of additional holes for adjusting the angle, and I would see it as pretty trivial to attach a stabilizing piece of steel. The steel would have to be pretty solid though. Or if you’re willing, you could just add an entire additional bottom plate/board, though that would add height, and with the riser, it’s already a pretty tall contraption. Alternatively, it’s possible to go all-in on making your own riser, such as this example: Module template CAD drawings - #10 by monguin
Here’s a picture of this morning’s experiment
